BULLETIN  No.  23. 


(B.  A.  I.  117.) 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY. 


0  =  • 
2  = 

|=  |i  SI- RUM  TREATMENT  OF  SWINE  PLAGUE 
AND  HOG  CHOLERA. 


E.  A.  deSCHWEINITZ,  Ph.  D.,  M. 

of  Biochemic  Division, 


Collaboration  of  Marion  Dorset,  M.  D.,  and  E.  C.  Schroeder.  M.  D.  V.. 

UNDER  THE  SUPERVISION  OF 

D.  E.  SALMON,  D.  V.  M., 
Chief  of  th«  Bureau. 


WASHINGTON  : 

• .  •  •  \    1    I!  N  M  K  N  T     !•  K  I  N  T  I  X  « i     <  >  K  I •'  I  i    I 

L8M 


BULLETIN  No.  23. 


(B.  A.  I.  117.) 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY. 


THE  SERUM  TREATMENT  OF  SWINE  PLAGUE 
AND  HOG  CHOLERA. 


E.  A.  deSCHWEINITZ,  Ph.  D.,  M.  D., 

Chief  of  liiochetnic  Division, 


Collaboration  of  Marion  Dorset,  M.  D.,  and  E.  C.  Schroeder.  M.  D.  V.. 


i:\DKR  THE  Sfl'KRVISlOX   OF 


D.  E.  SALMON,  D.  V.  M. 
Chief  of  the  liurean. 


WASHINGTON  : 

(io\  •  K  UN  M  KNT     I'KINTIMi     OKKIfK. 

1899. 


LETTER  OF  TRAXSMITTAL. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY, 
Washington,  D.  C.,  December  24,  1898. 

SIR:  Laboratory  investigations  in  the  use  of  serum  for  treating 
hog  cholera  and  swine  plague  have  been  carried  on  by  this  Bureau 
for  several  years,  and  with  such  favorable  results  that,  upon  your 
direction,  the  treatment  was  given  an  enlarged  field  in  Page  County, 
Iowa.  The  work  conducted  there  during  the  season  of  1897  showed 
that  the  treatment  saved  about  80  per  cent  of  the  animals  injected. 
The  results  in  1808  have  been  exceedingly  satisfactory  and  tend  to 
confirm  those  of  the  previous  year.  So  much  interest  has  been  mani- 
fested in  this  work  that  this  article  on  the  subject  of  serum  treat- 
ment for  hog  cholera  and  swine  plague  has  been  prepared  by  Dr.  de 
Schweinitz,  who  has  been  in  charge  of  the  work,  assisted  by  Dr. 
Marion  Dorset,  Dr.  E.  C.  Schroeder,  and  others,  and  its  publication 
as  a  bulletin  of  this  Bureau  is  recommended. 

The  public  should  be  informed  that  the  preparation  of  the  serum 
by  the  Bureau  is  necessarily  limited,  and  therefore  its  distribution 
is  confined  to  inspectors  for  the  Bureau  and  to  experiment  stations. 
Respectfully, 

D.  E.  SALMON, 
Chief  of  Bureau. 

Hon.  JAMES  WILSON, 

Secretary. 


TABLE  OF  CONTENTS. 


Page. 

Preliminary  experiments 5 

Results  of  experiments  with  serum  as  a  curative  agent - 7 

The  preparation  of  the  serum. 10 

The  preparation  of  a  mixed  serum 12 

Character  of  immunity 12 

Difficulties  of  field  work 12 

Practical  work  in  Page  County  in  1897  and  1898 13 

Expense  of  the  serum  preparation. 17 

Sources  of  infection 17 

Necessity  of  disinfection 17 

Legal  supervision  of  the  preparation  of  serum 18 


THE  SERUM  TREATMENT  FOR  SWINE  PLAGUE  AND 
HOG  CHOLERA. 

By  E.  A.  DE  SCHWEINITZ,  Ph.  D.,  M.  D., 
Chief  of  Biochemic  Division. 

One  of  the  most  interesting  and  difficult  problems  which  has 
engaged  the  attention  of  this  Bureau  for  some  years  has  been  the 
discovery  of  a  method  or  methods  for  the  prevention  or  cure  of  dis- 
eases known  as  hog  cholera  and  swine  plague  among  swine. 

PRELIMINARY   EXPERIMENTS. 

In  the  year  1890  a  study  of  the  substances  secreted  by  the  hog 
cholera  and  swine  plague  germs  was  begun  in  the  Biochemic  Labora- 
tory of  the  Bureau  of  Animal  Industry  by  the  writer  of  this  article. 
From  cultures  of  these  bacteria  he  succeeded  in  isolating  two  sub- 
stances albuminoid  in  character  and  others  belonging  to  the  group 
called  amines,  which  produced,  when  injected  into  experimental  ani- 
mals, some  of  the  characteristic  symptoms  of  hog  cholera  or  swine 
plague,  respectively,  and  conferred  upon  these  animals  an  immunity  to 
subcutaneous  inoculation  with  hog  cholera  and  swine  plague  germs, 
respectively.  The  reports  of  this  work  were  published  in  the  Medical 
News  of  Philadelphia  in  September  and  October,  1890,  and  annual 
reports  of  this  Department  for  1890  and  1891. 

A  series  of  practical  experiments  were  then  carried  on  at  the  experi- 
ment station  of  the  Bureau  upon  swine.  The  animals  were  injected 
with  the  products  of  the  growth  of  these  bacteria,  including  the  con- 
tents of  the  cells  themselves,  as  well  as  those  products  of  excretion 
of  the  cells  which  were  in  solution  in  the  culture  liquid.  In  ten  days 
after  inoculation  the}*  were  exposed  to  hog  cholera  and  swine  plague, 
respectively,  by  an  intravenous  inoculation  with  a  virulent  germ  suf- 
ficient in  quantity  to  kill  the  check  animals  in  a  week  to  ten  days. 
In  general  these  results  were  fairly  satisfactory,  in  so  far  that,  while 
the  check  animals  died,  about  oO  per  cent  of  the  treated  animals 
remained  alive.  The  method  of  exposure,  however,  was  unsatisfac- 
tory, as  it  was  not  always  {xjssihlt*  to  be  certain  that  the  checks  would 
die,  and  in  a  good  many  cases  the  exposure  of  the  treated  animals 
by  this  method  of  inoculation  was  very  much  more  severe  than  that 
which  they  would  in  all  probability  have  been  subjected  to  in  the  field. 
In  addition,  the  injection  of  these  products  of  the  bacilli  produced 
disagreeable  local  lesions  in  the  animals. 

While  the  results  of  the  work  showed  that  considerable  immunity 
to  these  diseases  could  be  secured  by  this  method  of  treatment,  it 
did  not  appear  practicable  for  field  work,  and  consequently  other  lab- 
oratory investigations  were  begun. 


6 

A  more  thorough  study  of  the  substances  produced  by  the  hog 
cholera  germ,  the  results  of  which  were  published  in  the  Philadelphia 
Medical  News  of  October,  1892,  showed  that  if  the  cultures  of  this 
germ  were  made  upon  milk  or  other  suitable  media,  it  was  possible  to 
obtain  from  these  cultures  a  small  quantity  of  enzyms,  or  soluble  fer- 
ments. These  ferments  secreted  by  the  hog  cholera  bacillus  were 
also  tried  for  the  purpose  of  producing  immunity  in  experimental 
animals,  with  satisfactory  results.  The  injection  of  quantities  of 
these  ferments  below  0.01  of  a  gram  was  without  ill  effect.  If  the 
amount  injected  was  increased  beyond  this  point  there  was  a  rise  of 
temperature  in  the  animals  for  several  days,  and  in  several  instances 
0.05  of  a  gram  was  sufficient  to  kill  the  animals.  A  single  injection 
of  guinea-pigs  with  0.04  of  a  gram  of  the  ferments  served  to  make 
the  animals  immune  to  an  inoculation  with  the  hog  cholera  germ  that 
was  sufficient  to  cause  the  death  of  the  checks  in  ten  days.  In  the 
article  referred  to  the  opinion  was  expressed  that  the  soluble  ferments 
exert  a  very  potent  action  in  rendering  animals  insusceptible  to  dis- 
ease, and  that  to  the  indirect  action  of  the  specific  ferments  secreted 
by  the  hog  cholera  and  other  germs  the  protective  and  curative  influ- 
ence of  blood  serum  from  immune  animals  may  be  traced,  as  well  as 
the  immunity  produced  by  injecting  animals  with  cell  contents  or  the 
products  of  the  cell  growth.  At  about  that  time  the  writer  published 
an  article  in  the  Philadelphia  Medical  News,  September  24,  1892, 
upon  the  production  of  immunity  in  guinea-pigs  to  hog  cholera  by  the 
use  of  blood  serum  from  other  guinea-pigs  that  had  been  previously 
immunized.  The  guinea-pigs  used  as  a  source  for  the  blood  serum 
were  immunized  by  means  of  the  cell  contents  and  products  of  the 
growth  of  hog  cholera  bacilli,  and  after  they  had  withstood  an  inocu- 
lation of  the  germ  of  sufficient  virulence  to  cause  the  death  of  the 
checks  they  served  as  a  source  of  serum  to  be  used  for  injecting 
other  healthy  guinea-pigs  or  for  treating  guinea-pigs  infected  with 
hog  cholera.  The  results  of  these  experiments  were  also  satisfactory, 
but  for  various  reasons  they  could  not  be  pushed  as  rapidly  as  desired. 
The  experiments  were  continued,  however,  in  a  quiet  way,  and  the  use 
of  the  products  of  other  bacteria  allied  to  the  hog  cholera  germ,  as 
the  Coli  communis,  etc.,  were  tried.  The  results  were  satisfactory 
for  the  purpose  of  securing  immunity  to  hog  cholera.  As  stated  in 
one  of  the  papers  mentioned,  it  is  probable  that  all  gas-producing 
bacilli  secrete  a  soluble  ferment,  and  that  this  ferment  is  of  consider- 
able importance  in  connection  with  the  production  of  immunity. 
While  it  is  not  probable  that  each  germ  gives  rise  to  a  distinctive 
ferment,  it  is  probable  that  different  germs  secrete  two  or  more  fer- 
ments, and  that  the  combined  action  of  these  ferments  is  necessary 
for  securing  satisfactory  results  in  immunity. 


RESULTS  OF  EXPERIMENTS  WITH  SERUM  AS  A  CURATIVE  AGENT. 

During  the  years  1893,  1894,  and  1895  it  was  possible  to  make  some 
more  experiments  with  the  serum  as  a  curative  agent  for  hog  cholera 
and  swine  plague  upon  a  somewhat  larger  scale.  Tfyese  experiments 
were  reported  to  the  Society  for  the  Promotion  of  Agricultural  Sci- 
ence in  Buffalo,  N.  Y.,  in  August,  1890,  and  published  in  their  pro- 
ceedings, in  the  New  York  Medical  Journal,  September  5,  1896,  and 
in  Centralbl.  f.  bakt.  u.  Parasit.,  Vol.  XX,  No.  16-17,  1896. 

The  animals  used  for  the  production  of  the  serum  were  treated 
for  me  by  Dr.  Schroeder,  in  charge  of  the  experiment  station  of  the 
Bureau. 

After  several  months'  injection  of  the  cows  with  the  virulent  hog 
cholera  culture,  the  serum  was  tested.  The  following  is  a  record  of 
one  of  the  experiments : 

Guinea-pigs  injected  with  sentm  from  treated  cows. 

March  9,  1894,  No.  219.  weight  17  ozs.,  received  1.5  c.  c.  of  serum. 
March  9,  1894,  No.  220,  weight  12  ozs.,  received  1.5  c.  c.  of  seruru. 
March  9,  1894,  No.  221,  weight  11  ozs.,  received  1.5  c.  c.  of  serum. 
March  9,  1894,  No.  222,  weight  17  ozs.,  received  1.5  c.  c.  of  serum. 

March  18,  1894,  No.  219,  weight  18  ozs.,  received  3  c.  c.  of  serum. 
March  18,  1894,  No.  220,  weight  11  ozs.,  received  3  c.  c.  of  serum. 
March  18,  1894,  No.  222,  weight  19  ozs.,  received  3  c.  c.  of  serum. 
March  18,  1894,  No.  223.  weight  14  ozs.,  received  3  c.  c.  of  serum. 

No.  221  was  found  dead  from  pneumonia  on  March  16. 
On  March  20  No.  220  was  found 'dead  from  pneumonia. 

March  23,  1894,  No.  219,  weight  17  ozs..  received  1.5  c.  c.  of  serum. 
March  23.  1894,  No.  222,  weight  17  ozs.,  received  3  c.  c.  of  serum. 
March  23,  1894,  No.  242,  weight  10*  ozs.,  received  3  c.  c.  of  serum. 
March  23,  1894,  No.  243,  weight  UH  ozs.,  received  3  c.  c.  of  serum. 
March  23,  1HJI4,  No.  24(5,  weight  9 A  ozs.,  received  3  c.  c.  of  serum. 

March  28,  1894,  No.  219.  weight  18  ozs.,  received  4.5  c.  c.  of  serum. 
March  2H,  1894,  No.  222,  weight  18  ozs.,  received  (5  c.  c.  of  serum. 
March  28,  1894,  No.  223.  weight  13  ozs.,  received  4  c.  c.  of  serum. 
March  28,  1H94,  No.  242,  weight  12  ozs.,  received  3  c.  c.  of  serum. 
March  2H,  1N94.  No.  243,  weight  12  ozs..  received  3  c.  c.  of  serum. 
March  2*.  1H»4.  No.  24«>.  weight  11  ozs..  received  3  c.  c.  of  serum. 

On  April  !i  the  following  guinea-pigs  were  inoculated  with  one- 
tenth  cubic  centimeter  of  pvptoni/.ed  beef-broth  hog  cholera  culture 
each  : 

No.  219.  weight  23  ozs.  No.  2K1.  weight  12  ozs. 

No.  222.  weight  IHozs.  No.  2«i2,  weight  15  ozs. 

No.  223.  weight  12  ozs.  No.  263.  weight  20  ozs. 

No.  242.  weight  13  OZH.  No.  2<H,  weight  14  ozs. 

No.  243.  weight  13  ozs.  No.  211.  weight  15  o/.s.  (check). 

No.  24«5.  weight  12  ozs.  No.  2Uo.  weight  12  ozs.  (check). 


8 

Nos.  261,  262,  263,  and  264  had  not  received  previous  injections 
with  serum;  241  and  260  were  checks;  while  the  other  animals  had 
been  treated  with  serum  as  above  noted. 

April  11,  No.  261  received  3  c.  c.  of  serum. 

April  11,  No.  262  received  3  c.  c.  of  serum. 

April  11,  No.  268  received  5  c.  c.  of  serum. 

April  11,  No.  264  received  4.5  c.  c.  of  serum. 

April  14,  No.  261  received  3  c.  c.  of  serum. 
April  14,  No.  262  received  3  c.  c.  of  serum. 
April  14,  No.  263  received  4.5  c.  c.  of  serum. 

The  result:  April  17,  No.  260  (check)  was  found  dead  from  hog 
cholera;.  April  10,  No.  222  was  found  dead  from  hog  cholera;  April 
20,  No.  264  was  found  dead  from  hog  cholera;  April  25,  No.  241 
(check)  was  found  dead  from  hog  cholera;  Nos.  219,  223,  and  261 
were  also  found  dead  from  pneumonia.  There  had  been  quite  an 
outbreak  of  pneumonia  among  the  guinea-pigs  just  at  this  time, 
accounting  for  these  lesions  which  were  not  due  to  cholera. 

Of  the  entire  number  of  pigs  treated,  therefore,  the  checks  died  in 
from  8  to  16  days.  Three  of  the  pigs  that  had  previous!}'  been  vac- 
cinated with  0  c.  c.  of  serum  each  recovered  and  two  of  the  pigs  that 
had  received  6  and  8  c.  c.  of  serum  two  days  after  the  inoculation 
with  the  germ  recovered  from  the  disease.  These  experiments 
repeated  later  showed  that  while  the  blood  contained  a  curative  and 
protective  substance  the  quantity  present  at  the  time  would  not  cure 
disease  by  the  injection  of  several  small  doses.  Subsequently,  by 
continued  treatment  of  the  animals,  the  curative  material  was  in- 
creased in  quantity,  as  will  be  seen  from  experiments  reported  later. 

Already  in  1894  some  work  had  been  done  which  served  to  empha- 
size the  close  relationship  between  the  products  in  artificial  media  of 
the  growth  of  the  hog  cholera  germ  and  those  produced  by  the  growth 
of  the  bacillus  Coli  communis  (the  ordinary  intestinal  bacillus).  A 
pig  which  had  been  immunized  to  hog  cholera  by  long-continued 
injections  of  the  Coli  communis  and  subsequently  inoculated  with 
the  hog  cholera  germs  was  used  as  a  source  for  the  serum  for  treat- 
ing guinea-pigs,  as  follows : 

No.  425,  weight  11  ozs.,  received  3  c.  c.  of  senim. 
No.  426,  weight  9  ozs.,  received  4.5  c.  c.  of  serum. 
No.  422,  weight  9  ozs.,  received  0.5  c.  c.  of  serum. 
No.  423,  weight  11  ozs.,  received  1.5  c.  c.  of  serum. 
No.  424,  weight  8  ozs..  received  2  c.  c.  of  serum. 

Fifteen  days  afterward  these  pigs  and  two  checks,  Nos.  442  and  443, 
were  inoculated  with  one-tenth  cubic  centimeter  of  a  peptonized  beef- 
broth  hog  cholera  culture  one  day  old.  Seven  and  10  days,  respect- 


ively,  after  this  inoculation  the  checks  were  found  dead  from  hog 
cholera  while  the  other  guinea-pigs  remained  well.  These  experi- 
ments repeated  upon  another  set  of  animals  gave  about  the  same 
results,  which  showed  that  an  immunizing  substance  is  produced  in 
the  blood  of  a  hog  that  is  protected  against  the  cholera.  Another  set 
of  experiments,  the  details  of  which  need  not  be  reported  here,  showed 
that  while  the  hog  itself  might  be  immune  to  disease,  its  blood  serum 
may  have  lost  the  power  of  conferring  immunity  upon  other  animals. 
This  confirms  the  conclusion  with  reference  to  the  use  of  blood  serum 
in  other  diseases,  namely,  that  the  immunizing  principle  in  the  blood 
serum  can  best  be  obtained  if  the  animals  are  inoculated  from  time  to 
time  with  the  culture,  or  toxins.  So  long  as  the  animal  receives  con- 
tinued injection  of  the  cell  contents  or  products  of  the  germ  the 
immunity  of  that  particular  animal  continues,  and  in  addition  the 
antitoxic  substance  is  found  in  the  blood.  After  some  time  the  anti- 
toxic substance  may  no  longer  be  noted  in  the  blood,  or  only  in  small 
amounts,  while  the  immunity  of  the  individual  animal  from  which 
this  blood  is  obtained  may  still  continue.  The  antitoxic  substances 
are  apparently  the  products  of  cell  activity  only. 

These  experiments  with  the  serum  of  immune  hogs  and  the  serum 
of  cattle  and  horses  that  had  been  made  artificially  immune  war- 
ranted further  investigation. 

In  practice,  however,  it  is  found  that  hogs  are  exposed  not  only  to 
the  disease  of  hog  cholera  but  also  to  another  disease  called  swine 
plague,  both  of  which  may  occur  together  in  the  same  animal,  or 
there  may  be  an  outbreak  of  one  or  the  other  disease  alone.  As  the 
experiments  made  in  1801  with  the  products  of  the  swine  plague 
germ  as  obtained  from  artificial  media  had  shown  that  these  could 
be  used  as  immunizing  agents  it  was  very  reasonable  to  suppose, 
when  the  nature  of  the  disease  swine  plague  is  considered,  that  an 
antitoxic1  serum  for  this  disease  might  also  be  obtained.  A  cow  was 
used  as  the  source  of  the  serum  after  she  had  been  repeatedly  inocu- 
lated with  cultures  of  the  swine  plague  germ.  The  preliminary  tests 
of  this  serum  were  made  upon  rabbits.  One-tenth  cubic  centimeter 
of  a  jK'ptonized  beef-broth  culture  of  the  swine  plague  sufficient  to 
kill  a  rabbit  in  fifteen  to  eighteen  hours  was  used.  Several  sets  of 
experiments  showed  that  while  the  check  rabbits  were  killed  within 
the  specified  time  by  the  swine  plague  cultures,  others  could  IK'  kept 
alive  from  six  to  ten  days  longer  than  the  checks  by  the  injection 
of  tic.  c.  of  the  serum  |>er  pound  weight.  As  these  results  indicated 
that  antitoxic,  or  curative,  substances  were  present  in  the  serum,  its 

'  The  word  antitoxic  is  us«-«l  in  this  article  in  th<-  senst-  of  curative. 


10 

effect  was  tried  upon  guinea-pigs.  One-tenth  cubic  centimeter  of 
swine  plague  culture  was  used,  sufficient  to  kill  the  animals.  The 
experiments  gave  the  following : 

No.  348  (check),  weight  12  ozs.,  received  0.1  c.  c.  swine  plague  culture. 

No.  349.  weight  8  ozs.,  received  0.1  c.  c.  swine  plague  culture  and  3  c.  c.  serum. 

No.  350  (check),  weight  11  ozs.,  received  0.1  c.  c.  swine  plague  culture. 

No.  351,  weight  9  ozs.,  received  0.1  c.  c.  swine  plague  culture  and  6  c.  c.  serum. 

No.  35'2,  weight  8  ozs.,  received  0.1  c.  c.  swine  plague  culture  and  6  c.  c.  serum. 

While  the  check  animals  died  the  pigs  which  received  the  antitoxic 
serum  recovered,  about  G  c.  c.  per  pound  weight  being  required  to 
check  the  disease. 

With  the  assistance  of  Dr.  Dorset  I  next  endeavored  to  isolate  the 
antitoxic  principle  contained  in  the  serum,  according  to  a  method 
prescribed  by  Brieger  and  Boer1  for  the  isolation  of  diphtheria  anti- 
toxin, by  the  use  of  zinc  sulphate,  repeated  solution  in  sodium  hydrate 
and  precipitation  with  CO2.  In  this  way  from  t»0  c.  c.  of  serum  about 
0.152  gram  of  a  practically  ash-free  white  powder  was  obtained. 
The  antitoxic  properties  of  this  substance  when  tested  proved  to  be 
about  the  same  as  those  of  the  serum.  As  we  had  therefore  a  serum 
which  exhibited  antitoxic  or  curative  properties  for  hog  cholera,  and 
another  which  exhibited  antitoxic,  or  curative,  properties  for  swine 
plague,  it  was  of  interest  to  see  if  these  serums  would  be  of  use  in- 
terchangeably. The  result  showed,  however,  that  the  hog  cholera 
serum  protected  guinea-pigs  from  the  cholera  germ  but  not  from 
the  swine  plague  germ,  and  that  the  swine  plague  serum  protected 
or  cured  guinea-pigs  from  infection  with  the  swine  plague  germ  but 
not  from  the  hog  cholera  germ.  This  demonstrated  again  the  inde- 
pendent character  of  these  two  diseases,  attention  to  which  has  often 
been  drawn  in  previously  published  work. 

As  the  preliminary  experiments  so  far  reported  had  shown  that 
specific  antitoxic  serums  for  hog  cholera  and  swine  plague  could  be 
obtained,  the  work  was  carried  forwrard  on  a  somewhat  larger  scale, 
and  serums  secured  which  were  effective  in  much  smaller  doses  upon 
experimental  animals.  The  laboratorj*  results  seemed  to  warrant  a 
trial  of  this  method  in  the  field,  and  experiments  were  made  during 
the  summer  and  fall  of  1897  on  this  line  in  Page  County,  Iowa. 

THE    PREPARATION    OF   THE    SERUM. 

In  preparing  the  serum  for  this  work  we  have  used  cattle,  horses, 
mules,  donkeys,  etc. ;  the  animals  received  injections  of  the  filtered, 
sterile,  or  live  cultures  of  the  hog  cholera  germ  and  swine  plague 
germ,  respectively,  or  the  solutions  of  their  products,  including  cell 
contents,  extracts,  and  secretions.  These  injections  were  made  either 


'Zeit.  fur  Hyg.  u.  Infectionskrank.,  Bd.  XXI,  Pt.  2. 


11 

subcutaneously,  intravenously,  or  intra-abdoniiually,  or  a  combina- 
tion of  two  or  more  of  these  methods,  depending  upon  the  results 
obtained.  The  quantities  given  at  first  were  small,  but  increased 
gradually  until  large  amounts  of  the  material  used  could  be  injected 
without  bad  results.  This  treatment  of  the  animals  must  be  carried 
out  very  carefully  and  requires  six  to  eight  months'  time  before  the 
serum  is  sufficiently  potent  to  be  of  any  practical  use.  As  the  treat- 
ment continues  the  power  of  the  serum  to  check  the  motility  of  the 
hog  cholera  germ  increases  with  rapidity.  The  serum  of  animals 
treated  with  swine  plague  cultures  also  sometimes  checks  the  motility 
of  the  hog  cholera  germ.  The  value  of  the  serum  was  determined 
by  the  amount  of  serum  necessary  to  protect  or  cure  guinea-pigs  from 
an  inoculation  with  the  hog  cholera  germ  or  swine  plague  germ  suffi- 
ciently virulent  to  kill  the  check  animals  in  the  usual  time — a  week 
to  ten  days. 

The  details  of  the  method  of  treating  these  animals  for  preparing 
the  serum  which  were  the  results  of  numerous  conferences  between 
Dr.  Schroeder,  in  charge  of  the  experiment  station,  and  the  writer, 
will  be  given  in  another  publication.  Too  much  care  can  not  be 
observed  in  selecting, the  animals  and  in  observing  proper  precautions 
during  the  injections  with  the  different  products  of  the  cultures  that 
are  used  for  producing  in  the  animals  a  curative  serum.  The  testing 
of  the  serum,  as  already  noted,  was  usually  made  by  treating  animals 
that  had  been  previously  inoculated  with  a  fatal  dose  of  the  culture. 
This  method  of  testing  is  sometimes  not  altogether  satisfactory  so  far 
as  the  cholera  germ  is  concerned,  although  the  results  given  witli  the 
swine  plague  are  quite  satisfactory.  We  have  therefore  used  another 
method,  namely,  the  injection  of  a  quantity  of  the  products  of  the 
hog  cholera  germ  sufficient  in  quantity  to  kill  the  check  guinea-pigs, 
while  the  other  guinea-pigs  so  injected  and  treated  with  the  serum 
will  not  succumb.  This  method  promises  more  satisfactory  results, 
and  a  l>etter  basis  can  thus  be  secured  for  estimating  the  amount  of 
curative  serum  which  should  be  used  for  injecting  large  animals. 

In  order  to  keep  and  utilize  large  quantities  of  serum,  we  have 
found  it  very  convenient  to  concentrate  it,  and  by  making  use  of  well- 
known  principles  we  have  accomplished  this  by  freezing,  so  that  a 
more  concentrated  material  can  be  obtained  and  a  less  quantity  of 
serum  used  for  injecting  animals.  The  preparation  of  a  solid  serum 
or  an  extract  from  the  serum  of  the  active  products,  secured  by 
means  of  precipitation,  has  already  IMHMI  referred  to,  but  for  practi- 
cal purjK)ses  it  would  ap]x>ar  that  a  concentrated  s<»ruin  is  the  lx»st 
product  to  place  in  the  hands  of  the  individual  veterinarian.  If  our 
experiments,  continued  on  a  still  larger  scale,  give  as  satisfactory 
results  as  those  obtained  during  the  years  1*!)?  and  IHliH  (and  then- 
is  every  reason  to  hope  that  such  will  Ix?  the  case)  it  would  appear 


12 

that  we  have  at  hand  a  practical  method  which  may  be  used  for 
decreasing  very  materially  one  of  the  most  serious  losses  to  which 
the  farmer  is  subjected. 

THE    PREPARATION    OF    A    MIXED    SERUM     FOR   THE   TREATMENT   OF 
HOG    CHOLERA    AND    SWINE    PLAGUE. 

The  experiments  had  shown  that  the  serum  prepared  for  the  pur- 
pose of  curing  hog  cholera  was  useful  in  protecting  or  curing  small 
experimental  animals  from  hog  cholera  only,  and  that  serum  pre- 
pared for  the  purposes  of  curing  swine  plague  was  useful  in  protect- 
ing from  swine  plague  only.  Other  work  had  shown  that  if  experi- 
mental animals  infected  with  hog  cholera  were  treated  with  a 
mixture  of  anti-hog  cholera  and  anti-swine  plague  serum,  that  they 
responded  generally  a  little  bit  more  quickly  to  the  treatment. 
Efforts  were  made  therefore  to  prepare  in  one  and  the  same  animal 
a  double  serum,  as  it  may  be  called.  In  order  to  do  this,  the  animals 
which  were  to  serve  as  a  source  for  the  serum  were  injected  with 
hog  cholera  cultures  and  swine  plague  cultures,  or  their  products, 
alternately  or  together,  the  doses  being  gradually  increased  imtil 
enough  had  been  injected  to  impart  to  the  serum  the  desired  proper- 
ties. The  first  tests  upon  experimental  animals  showed  that  a  serum 
could  be  obtained  in  this  way  which  exerted  slight  curative  proper- 
ties for  both  hog  cholera  and  swine  plague.  The  serum,  how- 
ever, was  more  active  in  checking  swine  plague  than  in  checking  hog 
cholera.  The  treated  animals  did  not  thrive  under  this  treatment. 
The  work,  however,  indicated  the  possibility  of  perhaps  producing  in 
the  same  animal  a  serum  which  may  be  specific  for  two  distinct  dis- 
eases. Experiments  are  being  made  now  to  ascertain  to  what  extent 
this  principle  can  be  utilized  in  connection  with  other  diseases  of  men 
and  animals,  especially  tuberculosis. 

CHARACTER   OF   IMMUNITY. 

The  length  of  immunity  produced  by  the  injection  of  serum  is  short 
and  more  permanent  immunity  can  apparently  be  secured  by  using 
in  addition  to  serum  the  products  of  the  germs.  The  serum  has 
appeared  most  efficacious  in  treating  herds  where  the  disease  had 
just  begun. 

DIFFICULTIES    IN    FIELD    WORK. 

A  very  important  difficulty  which  is  encountered  in  field  work  is 
that  it  is  almost  impossible  to  determine  in  the  field  whether  animals 
are  suffering  from  hog  cholera  or  swine  plague,  or  from  a  mixed  in- 
fection, unless  a  careful  autopsy  has  been  made.  And  even  when 
this  is  done,  on  account  of  the  similarity  of  many  of  the  lesions  found 


13 

in  the  two  diseases,  it  is  necessary  to  resort  to  a  careful  bacte- 
riological examination  of  the  cultures  obtained  from  these  animals  in 
order  to  decide  whether  the  disease  dealt  with  is  hog  cholera  or  swine 
plague.  This  has  already  been  pointed  out  in  previous  publications 
of  this  Bureau.  On  account  of  this  practical  difficulty  the  idea  very 
natural^  suggested  itself  that  it  would  be  well  to  treat  animals  in 
the  field  with  a  curative  serum  for  hog  cholera  mixed  with  a  curative 
serum  for  swine  plague  obtained  from  different  animals  or  with  a 
mixed  serum  produced  in  the  same  animal,  as  has  been  already  noted. 
The  quantity  of  the  serum  used  for  treating  pigs  weighing  from  40  to 
GO  pounds  was  10  c.  c.  When  the}*  were  heavier  a  larger  quantity 
was  used.  In  general,  in  the  experimental  as  well  as  the  practical 
work  that  has  been  done  by  the  Bureau,  a  single  injection  of  the 
serum  was  all  that  was  given  to  each  animal.  Unless  the  serum  to 
be  used  for  this  work  is  of  such  strength  that  one-half  to  1  c.  c.  of  it 
will  protect  a  500-gram  guinea-pig  from  a  fatal  inoculation  with  hog 
cholera  or  swine  plague  it  is  not  suitable  for  practical  work. 

WORK    IX    PAGE   COUNTY,    IOWA,    IX    1897. 

The  Secretary  of  Agriculture  requested  the  Governor  of  Iowa  to 
designate  a  county  of  the  State  of  Iowa  in  which  he  would  like  to 
have  experimental  work  carried  on  by  the  Bureau  of  Animal  Indus- 
try. The  Governor  selected  Page  County.  The  serum  for  treatment 
was  prepared  according  to  the  methods  that  have  been  previously 
noted,  conjointly  under  the  direction  of  Dr.  Schroeder,  in  charge  of 
the  experiment  station  of  the  Bureau  of  Animal  Industry,  at  Wash- 
ington, and  the  writer,  in  charge  of  the  Biochemic  Laboratory.  The 
field  work  in  Page  County  was  in  direct  charge  of  Dr.  Marion  Dorset. 
The  methods  of  treatment  used  were  the  following :  Sick  animals 
were  inoculated  with  serum  that  had  been  found  in  the  laboratory  to 
be  effective  against  either  hog  cholera  or  swine  plague,  or  the  swine 
were  inoculated  with  mixed  serums,  or  they  were  inoculated  with  the 
serums  to  which  had  l>een  added  the  products  of  the  hog  cholera  and 
swine  plague  bacteria  and  their  cell  contents,  or  cultures  in  which  the 
germs  had  been  killed  without  the  application  of  heat,  that  might 
in  any  way  have  affected  the  secretions  of  the  germ. 

In  order  properly  to  note  the  efficiency  of  field  work  of  this  sort  it 
is  very  important  that  a  large  number  of  checks  should  be  preserved. 
To  accomplish  this"  in  some  instances  a  portion  of  the  treated  herd 
was  reserved  and  not  given  scrum.  In  other  instances  herds  in 
which  disease  existed  of  about  the  same  virulence  as  that  in  the 
treated  herds  were  left  as  checks. 

The  conditions  under  which  animals  are  placed  in  all  diseases  of 
course  influence  very  greatly  the  results  for  the  methods  of  treatment 
used.  A  child  sick  with  diphtheria  may  be  given  an  injection  of  anti- 


14 

toxic  serum,  but  if  after  this  injection  the  child  is  otherwise  neglected 
it  will  in  all  probability  not  recover,  as  while  the  antitoxin  counteracts 
the  specific  poison  of  the  diphtheria  germ  it  does  not  give  the  further 
stimulation  to  the  system  which  is  also  necessary  for  recovery.  The 
case  is  similar  in  the  diseases  of  animals.  They  should  also  be  given 
proper  care  as  to  food,  water,  proper  housing,  and  a  moderate  degree 
of  cleanliness  if  any  method  of  treatment  whatsoever  is  to  prove  satis- 
factory. Very  often  the  farmer  has  himself  to  blame  quite  as  much 
as  an  outbreak  of  some  particular  disease  for  the  loss  which  takes 
place  in  his  herd.  If  he  treats  his  animals  as  inanimate  he  must 
not  be  surprised  if  they  finally  become  inanimate,  nor  can  he  hope 
that  when  they  are  almost  dead  the  administration  of  some  remedy 
will  miraculously  serve  to  revive  them.  In  many  instances  where 
the  animals  used  in  this  work  were  treated  the  farms  were  in  a  very 
good  condition  and  the  owner  exhibited  a  sufficient  amount  of  inter- 
est, care,  and  intelligence  to  warrant  successful  results.  In  other 
cases  the  farms  were  very  poor  and  the  farmers  seemed  indifferent  as 
to  whether  their  hogs  had  anything  to  eat  or  drink  for  two  or  three 
days.  In  order  therefore  to  give  the  fairest  test  possible  to  the 
method  of  serum  treatment,  the  better  farms  were  the  ones  reserved 
for  checks. 

FIELD   WORK   IN    1897. 

To  give  the  general  results  with  the  work  carried  out  under  the 
direction  of  Dr.  Dorset,  it  may  be  stated  that  out  of  100  animals 
treated  with  the  mixed  serums  161  were  saved,  or  about  82  per 
cent.  The  disease  existed  on  all  of  the  farms  where  treatment  was 
carried  out,  a  number  of  animals  had  already  died,  and  about  50  per 
cent  of  the  animals  treated  were  ill  at  the  time  of  injection  with  the 
serum.  In  the  check  herds  there  were  originally  420  animals,  and 
the  disease  had  begun  both  in  these  check  herds  and  in  the  treated 
herds  about  the  same  time.  In  the  herds,  which  were  not  .treated, 
only  about  15  per  cent  of  the  animals  recovered.  Comparing  these 
two  sets  it  would  appear  that  the  serum  had  reduced  the  mortality 
about  07  per  cent.  It  is  understood,  of  course,  that  all  of  the  ani- 
mals were  under  the  same  conditions  after  treatment  as  before.  As 
a  rule,  the  animals  appeared  to  begin  to  improve  very  shortly  after 
the  injection  of  the  serum.  One  herd  was  treated  with  a  culture 
alone  without  any  serum.  Only  40  per  cent  .of  the  herd  so  treated 
was  saved.  In  another  case  a  herd  which  was  in  a  very  poor  con- 
dition at  the  time  of  inoculation  was  treated  with  a  mixed  swine 
plague  serum  and  a  dead  culture.  Eighty  per  cent  of  these  ani- 
mals was  saved,  while  in  a  third  similar  case  where  the  condition 
of  the  animals  was  very  poor,  only  30  per  cent  was  saved.  These 
results,  obtained  under  rather  adverse  conditions,  indicated  that 


15 

serum  injection  for  swine  diseases  could  be  practiced  with  a  fair 
degree  of  success  when  the  animals  are  intelligently  treated  with  a 
mixed  hog  cholera  serum  and  swine  plague  serum  and  bacterial 
products,  provided  these  serums  are  active.  The  material  used  in 
this  way  is  perfectly  harmless,  so  that  a  farmer  need  have  no  fear 
whatsoever  in  allowing  his  animals  to  be  injected ;  if  it  should  hap- 
pen not  to  effect  the  desired  cure  it  will  not  injure  the  animal  in  the 
slightest  degree.  In  general,  of  course,  the  sooner  the  treatment  of 
sick  animals  can  be  begun  the  better  will  be  the  results  of  the  treat- 
ment, but  unless  the  reliability  of  the  serum  has  been  carefully 
tested  and  established  experimentally,  it  does  not  necessarily  follow 
that  a  sick  animal  which  has  been  injected  with  a  serum  that  is  said 
to  be  efficacious  will  be  cured.  If  in  the  case  of  diphtheria  the  mor- 
tality has  been  reduced  50  per  cent  by  the  serum  treatment  after 
long  years  of  careful  trial  with  thousands  of  cases,  it  is  fair  to 
assume  that  this  method  of  treatment  of  swine  disease  is  worthy  of 
a  more  extensive  practical  experiment. 

The  character  of  the  disease  in  the  animals  treated,  as  well  as  in 
the  check  herds  in  the  year  1897,  was  determined  by  careful  autopsy 
or,  so  far  as  possible,  by  the  identification  of  the  cultures  made  from 
the  diseased  organs  of  some  of  the  animals  upon  which  autopsy  had 
been  performed.  In  most  of  the  cases  examined  the  hog  cholera  germ 
was  found  present,  and  specimens  of  blood  which  were  examined  for 
me  by  Dr.  Dawson,  Assistant  in  the  Division  of  Animal  Pathology 
of  this  Department,  gave  the  characteristic  reaction.  The  checking 
of  the  motility  of  the  hog  cholera  bacilli,  a  reaction  similar  to  that 
used  for  diagnosing  typhoid  fever,  as  has  been  suggested,  might  per- 
haps be  useful  in  determining  the  character  of  diseases  among  swine 
in  the  field  in  a  quicker  way  than  would  be  possible  if  it  was  necessary 
always  to  work  out  the  nature  of  the  culture.  While  the  majority 
of  these  blood  examinations  agreed  with  the  culture  tests,  in  a  few 
instances  the  characteristic  checking  of  the  motility  was  observed 
in  blood  taken  from  animals  which  undoubtedly  died  from  swine 
plague.  These  animals  may  have  had  in  addition,  however,  a  slight 
infection  with  hog  cholera.  At  any  rate,  in  chronic  cases  of  disease 
in  swine,  when  it  is  sometimes  difficult  to  succeed  in  transferring  to 
the  laboratory  a  virulent  culture  from  the  diseased  animals,  it  is  prob- 
able that  the  blood  test  may  be  of  service  as  a  diagnostic  agent. 

So  long  as  a  serum  is  being  used  which  has  curative  properties  for 
both  of  .the  diseases  to  which  the  animals  in  the  field  arc  usually  sub- 
jected, it  is  not  of  so  much  importance  to  IM>  able  to  make  a  positive 
diagnosis  or  distinction  between  the  two  diseases.  The  acutcncss  of 
the  attack  is  perhaps  of  more  importance,  as  it  serves  to  indicate  the 
amount  of  serum  which  should  IK>  used  in  treating  animals. 


16 

FIELD   WORK   IN   1898. 

As  the  laboratory  experiments  and  the  field  work  of  189?  already 
reported  had  given  such  encouraging  results,  at  the  request  of  The 
Hon.  James  Wilson,  Secretary  of  Agriculture,  Congress  made  a 
larger  appropriation  which  should  be  utilized  during  the  year  1898 
for  making  more  thorough  practical  tests  of  this  curative  serum 
for  swine.  Unfortunately  this  appropriation  was  not  made  availa- 
ble as  early  as  desirable.  It  was  necessary  after  the  needed  funds 
were  secured  to  erect  additional  stables  to  accommodate  the  large  num- 
ber of  animals  at  the  experiment  station  of  the  Bureau,  to  purchase 
the  animals  and  other  necessary  facilities  for  cariying  on  the  work. 
The  experimental  work  in  preparing  the  serum  therefore  could  not  be 
begun  before  the  first  of  June,  and  consequently  the  amount  of  serum 
ready  for  use  in  the  fall  of  1898  was  not  so  large  as  we  had  hoped, 
or  as  it  might  have  been  if  the  appropriation  had  been  available 
three  or  four  months  earlier,  when  it  was  requested.  Nevertheless, 
the  field  work  was  resumed  again  in  Page  County,  Iowa.  In  July, 
Dr.  McBirney,  an  inspector  on  the  Bureau  force,  was  put  in  charge 
of  the  work  in  that  coimt}r,  after  being  given  instructions  from  the 
laboratory  as  to  the  quantity  of  serum  to  be  used,  the  method  of  using 
it,  the  manner  of  treating  herds,  the  method  of  keeping  records,  and 
so  on.  This  work  was  carried  out  very  faithfully  by  Dr.  McBirney, 
according  to  the  general  directions  furnished  him,  and  the  results 
reported  up  to  date  (December  1,  1898)  have  been  exceedingly  satis- 
factory and  tend  to  confirm  the  results  obtained  in  the  year  1897. 
Between  the  13th  of  July  and  the  llth  of  November,  Dr.  McBirney 
treated  35  herds  containing  1,727  animals.  Of  these  treated  animals 
403  died — a  loss  of  23.10  per  cent  in  the  treated  herds.  Cultures  and 
specimens  of  blood  were  sent  to  the  laboratory  from  most  of  these 
herds,  and  in  1 7  of  the  herds  the  presence  of  the  hog  cholera  germ  was 
demonstrated  by  tests  upon  experimental  animals  as  well  as  by  a  care- 
ful study  of  the  cultures.  In  3  the  presence  of  the  swine  plague  germ 
was  demonstrated.  The  examination  of  the  blood  and  the  motility 
test  confirmed  the  presence  of  either  hog  cholera  or  swine  plague,  and 
indicated  its  presence  in  some  of  the  herds  the  cultures  from  which 
had  not  given  positive  results.  Autopsies  were  made  upon  one  or 
more  animals  in  each  of  these  herds  and  records  carefully  kept. 
They  indicated  in  many  instances  the  presence  of  acute  or  chronic 
hog  cholera,  in  a  few  cases  swine  plague,  or  a  combination  of  both 
diseases. 

Thirty-three  herds  in  whole  or  in  part  were  reserved  as  checks 
upon  those  which  were  treated.  In  some  of  these  herds  the  char- 
acter of  the  disease  was  also  demonstrated  by  cultures  or  blood  reac- 
tions. In  others  the  autopsy  indicated  the  character  of  the  disease 
and  hog  cholera  was  found  predominant.  The  number  of  animals  in 


17 

these  check  herds  was  3,197.  Of  these  only  GOO  survived,  or  81.24 
per  cent  was  lost.  This  shows  about  as  large  a  percentage  of  ani- 
mals saved  in  the  treated  herds  as  were  lost  in  the  nontreated  herds 
and  leaves  apparently  but  little  doubt  as  to  the  efficacy  of  practical 
treatment  of  swine  diseases  in  the  field  by  the  use  of  these  mixed 
serums  alone  or  with  bacterial  products,  combined  with  simple  meth- 
ods of  disinfection  and  slight  care  which  every  farmer  should  be  will- 
ing to  give  to  his  animals.  The  serum  is  intended  to  cure  disease 
simply,  and  should  have  such  aids  as  clean,  warm  quarters  and  good 
food  and  water;  it  is  no  protection  against  freezing,  smothering  or 
starvation. 

The  results  of  our  work  so  far  warrant  the  following  conclusions : 
Animals  treated  with  the  hog  cholera  germs,  their  cell  contents  and 
secretions  or  those  of  allied  germs  yield  a  serum  which  has  curative 
properties  for  hog  cholera.  Similar  results  are  obtained  for  swine 
plague  by  the  treatment  of  animals  with  the  germs  or  their  cell 
contents  and  secretions. 

The  most  satisfactory  results  in  field  work  have  been  secured  by 
treating  the  swine  with  a  curative  serum  for  swine  plague  mixed 
with  a  curative  serum  for  hog  cholera. 

LOSSES    FROM    HOG   CHOLERA    AND    SWINE   PLAGUE. 

It  is  estimated  that  the  State  of  Iowa  alone  loses  $15,000,000  per 
year  in  the  number  of  hogs  that  die  from  disease.  The  work, 
which  has  been  carried  on  as  above  reported,  indicates  that  at  least 
$1 1 ,000,000  of  this  loss  might  be  avoided  at  a  comparatively  slight  cost. 

EXPENSE  OF  THE  METHOD  OF  PREPARING  AND  USING  SERUM. 

The  farmer  should  be  able  to  have  his  hogs  injected  at  a  cost  not 
to  exceed  15  cents  per  head  if  the  material  for  this  purpose  is  pre- 
pared in  a  careful  and  legitimate  way — for  the  benefit  of  the  farmer 
rather  than  for  the  benefit  of  the  manufacturer.  If  the  latter  simply 
desires  to  reap  financial  profits,  irrespective  of  the  fact  that  his 
material  may  or  ma}'  not  be  useful,  the  results  will  undoubtedly  be 
disastrous.  Fifteen  cents  per  head  is  but  a  trifle  to  the  fanner  if  ho 
is  thereby  enabled  to  save  HO  to  SO  per  cent  of  his  animals  which 
would  otherwise  be  lost. 

SOURCES   OF    INFECTION    AND    NECESSITY    OF    DISINFECTION. 

The  fact  that  the  cause  of  infection  can  be  carried  from  one  farm 
to  another  by  animals,  by  birds,  by  water  running  through  several 
fanns  on  some  of  which  disease  exists,  by  tho  farmers  themselves 
visiting  the  pens  and  lots  where  their  neighbors  have  sick  hogs,  can 
not  be  too  strongly  emphasized.  Disinfection  of  the  premises,  of  the 
farmer's  boots,  clothing,  of  the  wagons,  etc.,  are  absolutely  neces- 


18 

sary.  Hence  in  all  cases  pens  and  lots  should  be  thoroughly  disin- 
fected with  lime  or  5  per  cent  carbolic  acid,  a  pure  water  supply 
should  be  secured,  and  the  hogs  should  from  time  to  time  have  access 
to  a  mixture  of  salt,  sulphur,  and  charcoal,  or  this  should  be  put  in 
their  food.  The  animals  should  also  have  access  to  comfortable, 
well-protected  sheds. 

STATE    SUPERVISION. 

The  results  of  the  experiments  conducted  by  the  Bureau  of  Animal 
Industry  indicate  the  advisability  of  certain  State  experiment  stations 
carrying  out  this  line  of  work  in  cooperation  with  the  Bureau  of 
Animal  Industry. 

Some  expense  is  necessary  for  starting  plants,  building  stables 
and  securing  the  animals,  and  a  good  deal  of  instruction,  for  the 
men  who  undertake  the  work  would  be  required.  At  the  same  time, 
as  these  experiment  stations  were  inaugurated  in  order  to  advance 
the  agricultural  interests  of  the  farmers,  as  they  receive  a  very  large 
amount  of  support  from  the  National  and  State  governments,  it  is 
presumed  that  they  will  gladly  cooperate  in  every  effort  to  promote 
the  interests  of  the  farmer.  Undoubtedly  commercial  firms  would 
be  only  too  anxious  to  take  up  the  manufacture  of  these  serums,  as 
the  loss  to  farmers  from  these  diseases  of  swine  is  so  enormous. 
The  moment  that  products  of  this  sort,  which  can  be  so  easily  put  up 
in  a  condition  that  they  may  be  perfectly  worthless  and  still  appear 
satisfactory,  are  placed  on  the  market  for  gain,  the  temptation  is  so 
great  to  sell  an  inefficient  material  that  very  often  unsatisfactory 
results  may  be  obtained  and  great  discredit  thrown  upon  the  entire 
work.  If  private  firms  undertake  the  manufacture  and  sale  of -serum 
for  treating  swine,  their  products  and  prices  should  be  subject  to 
legal  supervision.  If  the  public  is  protected  against  the  sale  of 
utterly  worthless  fertilizers,  as  is  the  case  in  many  of  our  States,  most 
assuredly  the  sale  of  a  material  which  may  prove  so  essential  to  the 
farmer  should  also  be  subject  to  legislative  control.  No  lot  of  serum 
should  be  sold  unless  it  had  been  approved,  and  its  value  as  a  curative 
agent  tested,  by  careful  official  inspection  and  trial.  As  the  Bureau  of 
Animal  Industry  has  now  a  plant  for  the  manufacture  of  this  mate- 
rial, has  obtained  a  great  deal  of  very  valuable  experience,  and  has 
worked  out  the  theoretical  and  some  of  the  practical  principles  of  the 
use  of  serum  which  promises  such  good  results  in  treating  swine,  it 
is  probable  that  for  several  years  to  come  at  least  those  who  are 
working  along  these  lines  will  prefer  that  the  control  of  this  material 
should  remain  either  directly  in  its  hands  or  under  its  supervision. 
The  Bureau  is  endeavoring  to  push  the  work,  and  to  supply  larger 
and  still  larger  quantities  of  serum  for  use,  and  will  carefully  note 
and  report  the  results. 


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